What do the jellyfish eat and how do they digest? How their gastrovascular system works

The jellyfishoften feared for stings and theirs I wait, they are marine animals belonging to Phylum of the Cnidariwhich hide a complex and fascinating world. Although composed for beyond 90% waterhave a gastrovascular system advanced that allows them to hunt zooplankton (Plancton composed of animal organisms), crustaceans And fish use cnidocisti poisonous to immobilize the prey. Some species, such as Rhizostoma Pulmoexploit more sophisticated food strategies with multiple “mouths” along the tentacles To ingest and digest food. These mechanisms reveal an intricate evolution that goes beyond the apparent simplicity of these carnivorous sea creatures. In this article we therefore see what the jellyfish feeds on and with what mechanisms.

A small but important clarification: In common speech we mean jellyfish those gelatinous marine organisms in the shape of a bell, with many beautiful stinging tentacles. In zoology this definition (rather vague) should be integrated with an important more detail. The term Medusa refers to a specific and mobile phase of the life cycle of these animals (medusoid phase) which alternates with the sessile phase and anchored to the seabed (polypoid phase). In this article we will call the boats “with the hat” and the mouth facing downwards, polyps, the colonial and bentonic ones with the mouth facing upwards.

Power supply of jellyfish and capture methods

The jellyfish are often dodged, even “disgusted” for their gelatinous consistency or their nature stinging, but they play a fundamental role in marine ecosystems as well as being very animals complex and rich in characters and peculiarities to discover. One thing that is mistakenly taken for granted in jellyfish is the almost absence of organs, being made over 90% by water. What if we told you that it is not so? Have a Very complex gastrovascular system that allows them to be swimming and to feed.

Most of the jellyfish is carnivore: although they can also feed on small algae, their diet is mainly composed of other animals. Among these are all organisms belonging to the zooplankton as well small crustaceans and fish that capture with the cnidocistiingenious predatory bodies that have both defensive and offensive function.

These structures work like small soaked needles of poison that are fired mechanically like a deer to stun the opponents and make them unable to move. They work with mechanoreceptors that activate the extroflegation of stinging filaments called cnidi who can even kill small prey for anaphylactic shock. This procurement mechanism guarantees the partial immobility of the prey and facilitates entry into the mouth.

The substances injected can be more or less dangerous for humans even if, fortunately, jellyfish “stings” are not so serious: they create Burn and Strying But they are easily treated with appropriate easily available creams. The really curious thing about the way of feeding these animals lies in the structure and in the number of mouths: The vast majority of the species has a single central mouth, others (including those belonging to the Rhizostomatidae family) have many mug openings along the tentacles.

A single opening for everything

The vast majority of jellyfish owns A single opening in the lower part of the bodyunder the bell, also called umbrella. In this very simple digestive system, there is no real difference between intestine and stomach and opening has a double function: It is both a mouth and an anus. During the feeding the prey is first blocked thanks to the poisons released by the Cnidocists or the stinging mucus and then addressed to the basal part of the umbrella, where the central mouth is located. At this point the digestion takes place by enzymes produced inside the cavity and the waste are expelled.

In some species, however, youth individuals change the way to feed each other: initially they use the central mouth, but then this closes permanently and develop alternative digestive channels.

The jellyfish that eat with the tentacles

Having a mouth is almost trivial, don’t you find? All animals somehow have it, it is used to feed. In the jellyfish the question becomes particularly interesting when complexity increases and a two -way systemwith openings dedicated to the entry of food and others dedicated to the waste. But it does not end here: the focal point of the speech is the place where these characters are found: the gastrovascular system of some jellyfish is located within the tentacles.

These structures, better called oral armshave both Motile and predatory function, and food. In a nutshell, some species ingest food through the countless mouths that are located along the arms And, in the same way, they use other channels as output orifices.

What enters then passes to the gastric cavity and the stomach within the “head” of the jellyfish, is digested and then discarded through the countless ani which has the animal. A species that uses this mode is the Municipality sea ​​lung (Rhizostoma Pulmo), typical of the Adriatic Sea and the Mediterranean.

A recent study published in Plosone shows how the morphological and functional characterization of the gastrovascular system Of Rhizostoma Pulmo (Macri 1778), designed in detail with innovative techniques (resin endocalchi and computing microtomography with X 3D rays) may provide us with important information on Power methodsi phylogenetic relationships with other species and theecology of these animals.